src/main/java/org/apache/log4j/xml/LogFileXMLReceiver.java

/*
 * Copyright 1999,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.apache.log4j.xml;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Collection;
import java.util.Iterator;

import org.apache.log4j.helpers.Constants;
import org.apache.log4j.plugins.Receiver;
import org.apache.log4j.rule.ExpressionRule;
import org.apache.log4j.rule.Rule;
import org.apache.log4j.spi.Decoder;
import org.apache.log4j.spi.LoggingEvent;

/**
LogFileXMLReceiver will read an xml-formated log file and make the events in the log 
file available to the log4j framework.  

<p>This receiver supports log files created using log4j's XMLLayout, as well as 
java.util.logging XMLFormatter (via the org.apache.log4j.spi.Decoder interface).

<p>By default, log4j's XMLLayout is supported (no need to specify a decoder in that case).

<p>To configure this receiver to support java.util.logging's XMLFormatter, specify a
'decoder' param of org.apache.log4j.xml.UtilLoggingXMLDecoder.

<p>Tailing -may- work, but not in all cases (try using a file:// URL).  If a process has a log file open,
the receiver may be able to read and tail the file.  If the process closes the file and reopens the file, 
the receiver may not be able to continue tailing the file.

<p>An expressionFilter may be specified.  Only events passing the expression will be forwarded to the log4j framework.

<p>Once the event has been "posted", it will be handled by the
appenders currently configured in the LoggerRespository.

@author Scott Deboy <sdeboy@apache.org>

  @since 1.3
*/

public class LogFileXMLReceiver extends Receiver {
	private String fileURL;
	private Rule expressionRule;
	private String filterExpression;
	private String decoder = "org.apache.log4j.xml.XMLDecoder";
	private boolean tailing = false;

	private Decoder decoderInstance;
	private Reader reader;
	private static final String FILE_KEY = "file";
	private String host;
	private String path;

	/**
	 * Accessor
	 * 
	 * @return file URL
	 */
	public String getFileURL() {
		return fileURL;
	}

	/**
	 * Specify the URL of the XML-formatted file to process.
	 * 
	 * @param fileURL
	 */
	public void setFileURL(String fileURL) {
		this.fileURL = fileURL;
	}

	/**
	 * Accessor
	 * 
	 * @return
	 */
	public String getDecoder() {
		return decoder;
	}

	/**
	 * Specify the class name implementing org.apache.log4j.spi.Decoder that
	 * can process the file.
	 * 
	 * @param _decoder
	 */
	public void setDecoder(String _decoder) {
		decoder = _decoder;
	}

	/**
	 * Accessor
	 * 
	 * @return filter expression
	 */
	public String getFilterExpression() {
		return filterExpression;
	}

	/**
	 * Accessor
	 * 
	 * @return tailing flag
	 */
	public boolean isTailing() {
		return tailing;
	}
	
	/**
	 * Set the 'tailing' flag - may only work on file:// URLs and may stop tailing if the 
	 * writing process closes the file and reopens.
	 * 
	 * @param tailing
	 */
	public void setTailing(boolean tailing) {
		this.tailing = tailing;
	}
	/**
	 * Set the filter expression that will cause only events which pass the filter
	 * to be forwarded to the log4j framework.
	 * 
	 * @param filterExpression
	 */
	public void setFilterExpression(String filterExpression) {
		this.filterExpression = filterExpression;
	}

	private boolean passesExpression(LoggingEvent event) {
		if (event != null) {
			if (expressionRule != null) {
				return (expressionRule.evaluate(event));
			}
		}
		return true;
	}

	public static void main(String[] args) {
		/*
		LogFileXMLReceiver test = new LogFileXMLReceiver();
		test.setFileURL("file:///c:/samplelog.xml");
		test.setFilterExpression("level >= TRACE");
		test.activateOptions();
		*/
	}

	/**
	 * Close the receiver, release any resources that are accessing the file.
	 */
	public void shutdown() {
		try {
			if (reader != null) {
				reader.close();
				reader = null;
			}
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}
	}

	/**
	 * Process the file
	 */
	public void activateOptions() {
		new Thread(new Runnable() {
			public void run() {
				try {
					URL url = new URL(fileURL);
					host = url.getHost();
					if (host != null && host.equals("")) {
						host = FILE_KEY;
					}
					path = url.getPath();
				} catch (MalformedURLException e1) {
					// TODO Auto-generated catch block
					e1.printStackTrace();
				}

				try {
					if (filterExpression != null) {
						expressionRule = ExpressionRule
								.getRule(filterExpression);
					}
				} catch (Exception e) {
					getLogger()
							.warn(
									"Invalid filter expression: "
											+ filterExpression, e);
				}

				Class c;
				try {
					c = Class.forName(decoder);
					Object o = c.newInstance();
					if (o instanceof Decoder) {
						decoderInstance = (Decoder) o;
					}
				} catch (ClassNotFoundException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (InstantiationException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}

				try {
					reader = new InputStreamReader(new URL(getFileURL())
							.openStream());
					process(reader);
				} catch (FileNotFoundException fnfe) {
					getLogger().info("file not available");
				} catch (IOException ioe) {
					getLogger().warn("unable to load file", ioe);
					return;
				}
			}
		}).start();
	}

	private void process(Reader unbufferedReader) throws IOException {
		BufferedReader bufferedReader = new BufferedReader(unbufferedReader);
		char[] content = new char[10000];
		getLogger().debug("processing starting: " + fileURL);
		int length = 0;
		do {
			System.out.println("in do loop-about to process");
			while ((length = bufferedReader.read(content)) > -1) {
				processEvents(decoderInstance.decodeEvents(String.valueOf(content,
						0, length)));
			}
			if (tailing) {
				try {
					Thread.sleep(5000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		while (tailing);
		getLogger().debug("processing complete: " + fileURL);

		shutdown();
	}

	private void processEvents(Collection c) {
		if (c == null) {
			return;
		}

		for (Iterator iter = c.iterator(); iter.hasNext();) {
			LoggingEvent evt = (LoggingEvent) iter.next();
			if (passesExpression(evt)) {
				if (evt.getProperty(Constants.HOSTNAME_KEY) != null) {
					evt.setProperty(Constants.HOSTNAME_KEY, host);
				}
				if (evt.getProperty(Constants.APPLICATION_KEY) != null) {
					evt.setProperty(Constants.APPLICATION_KEY, path);
				}
				doPost(evt);
			}
		}
	}
}